Stabilized lubricating emulsions



Patented June 10, 194

STABILIZED LUBRICATING EMULSI ONS Malcolm D. Bray, Fishkill, N. Y., assignor to The ration of Delaware Texas Company, New York 17, N. Y., a corpo- No Drawing. Application August 31, 1944,

v Serial No. 552,203

7 Claims. (01. 252-495) This invention relates to a stable oil-in-water emulsion and particularly to an emulsified lubricating composition suitable for the lubrication I of air compressors and the like.

It has been found that a guanidine salt of a carboxylic acid possessing at least 10 carbon atoms, such as a soap-forming fatty acid, is an efficient emulsifying and thickening agent for oil-in-water emulsions. The oil-in-water emulsions, which are emulsified by the incorporation of small amounts of guanidine stearate. are unusually stable at atmospheric temperatures, but are inclined to separate at elevated temperatures. The addition of the guanidine salt also causes a thickening eflect, thereby providing an oil-in-water emulsion of varying consistency, depending upon the amount of guanidine salt used.

Oil-in-water emulsions have been recognized as particularly advantageous in the lubrication of metal surfaces where the temperatures encountered are sufiilcient to volatilize the lubricating oil. Suchtemperatures are generally in the range of 500-1000" F. The lubricating emulsions useful for this purpose are particularly the nonmetal emulsions, such as disclosed and claimed in U. S. Patent No. 2,353,830, issued to Gus Kaufman, Karl Uhrig, and Robert S. Barnett on July 18, 1944, This patent is directed to an oil-inwater lubricating emulsion in which the emulsifying agent is an alkylolamine soap of a higher fatty acid and the thickening agent is a free fatty acid. The use of this type of emulsion is attended with certain disadvantages in that the presence of the free fatty acid reduces the stability of the emulsion and renders the lubricant corrosive to copper and steel. Thesecorrosive tendencies result in a build-up of deposits and separation of the emulsion which ultimately cause uneven lubrication and seizure of lubrieating surfaces.

According to the presentinvention it has been discovered that an emulsion of an oil in water in which the emulsifying agent consists of the combination of a guanidine salt of ahigh molecu* lar weight fatty acid and an alkylolamine salt. of a carboxylic acid containing at leastten carbon atoms, possesses exceptional stability even at elevated temperatures and over long periods of storage. Stable emulsions of this type are useful for manypurposes such as spray bases, insecti cide bases dye baths,.flotation oils, cosmetic bases, and the like, but for the purpose of the present invention the followingdetailed descrip-. tion will be restricted to their application as lubricating emulsions.

A lubricating emulsion suited to the lubrication of air compressors and the like, is one which preferably is possessed of the following characteristics: Stability at atmospheric and elevated temperatures, optimum consistency to provide a satisfactory feeding rate, minimum corrosive action on metals used in the lubrication system, minimum residue upon volatilization, and detergent or cleaning action upon carbonaceous deposits formed on lubricating surfaces.

A lubricant which substantially satisfies the above requirement is obtained from an emulsion of mineral oil in water with an emulsifying agent comprising the combination of guanidine stearate and triethanolamine stearate. In the lubrication of air pumps, where the lubricant is in contact with both copper and steel, it is preferable to use an emulsifying combinationin which the ratio of the guanidine salt to triethanolamine salt is greater than 1, and to include in the emulsion composition a small amount of free triethanolamine. The eflect of the larger proportions of guanidine salt and the addition of free triethanolamine is to obtain a strongly alkaline emulsion which is substantially noncorrosive to copper or steel.

The characteristics oflthe mineral oil component naturally vary. with the type of lubrication required of the emulsion, but in most instances it is preferable to select a low viscosity distillate oil in place of a high viscosity residual oil, due to the lower carbonaceous residues resulting from the volatilization of the distillate oils. For the best results in the lubrication of air compressors a petroleum oil is selected whose viscosity is within the range of -100SaybolthUniversal seconds at 210 F. Such an oil may be a single fraction or a mixture'of a high and low viscosity 10 carbon atoms, examples of which arelauric, palmitic, myristic, behenic acids and their dej rivatives, or mixtures thereof. The guanidine salts of unsaturated fatty acids, such as the oleate, are not suitable because of the-instability of the resulting emulsions. ,7 I v In place of triethanolamine ,stearate other alkylolamine salts of monocarboxylic acids may be used. The alkylolamines include the common; cial mixtures of the variousv ethanolamines f and. propanol amines, together with their alkylated" derivatives and other aliphatic amines known to be equivalent thereto. The monocarboxylic acids which form' the acidic constituent of the alkylolamine salts include the fatty acids and unsaturated fatty acids, such as palmitic and oleic acids and, in general, the aliphatic monocarboxylic acids containing at least ten carbon 1 atoms, together with mixtures thereof, maybe used.

As previously mentioned, it has been'found desirable to incorporate into the emulsion a small amount of free triethanolamine in order to provide a maximum resistance to corrosion of cop- .per and steel. Here again, other alkylolamines may be substituted therefor, and the usualpractise is to incorporate the same alkylolamine as is present in the salt. When the alkylolamine salt is prepared in situ, this is accomplished by adding a calculated quantity of alkylolamine in excess of that required to neutralize the monocarboxylic acid. The proportions of free alkylolamine in the emulsion composition may be as high as 1%, although the best balance between corrosive resistance and stability of the emulsion is obtained with a maximum of 0.5%.

A non-corrosive lubricating emulsion, particu: larly suited to the lubrication of railway air pumps, may be compounded within the following range of proportions:

I Per cent Organic salts (ratio .of guanidine to alkylolamine salt greater than 1) 1-15 Free alkylolamine 001-1 4 Mineral oil. -1 5-25 Water 59-9399 2.97 pounds of stearic acid (Saponification No.

210) and approximately 40 pounds of water were charged to a steam-heated kettle which is heated to 180-200" F. and stirred at a fairly rapid rate; 3.5" paddles rotating at 102 R. P. M., giving a peripheral speed of 187 ft. per minutewere used.

After the temperature was brought up to 180-200 F., 0.80 pound'of guanidine carbonate (95% pure), dissolved in a minimum amount of water, were added, with stirring over a period of approximately one hour. The addition of guanidine carbonate results in foaming and frothing of the mixturedue to the escaping carbon dioxide. The

' mixture was thenstirred until all the foam had disappeared and the gas had been worked out of the mixture. This stirring operation usually requires approximately one hour in laboratory kettles. Fifteen pounds of a pale oil having a viscosity of 88-92 Saybolt Universal seconds at 210 'F., were then added to the mixture as fast as it could be emulsified, which usually requires from 15 to 30 minutes. The mixture was then stirred for approximately 15 minutes in order to make certain that the mineral oil was completely emulsified. 0.703 pound of commercial triethanolamine were dissolved in sumcientwater' to make the total added water equal to 80.5% of the finished emulsion, and this solution was then added to the oil-wate'r emulsion over a period of approximately one hour. The temperature must be watched very closely during the addition of the triethanolamine in order to maintain the range of 180-200 F. The stirring rate wasthen reduced to a peripheral speed of 139 ft. per minute and the mixture allowedto cool to '100" F. or less before drawing. Maintaining the temperature of the mixture at 180 F. or above is imperative until the emulsion is formed, otherwise the guanidine stearateprecipitates. Water can be worked in at the drawing temperature, which is 100 F. or less, to compensate for anyloss during manufacture. The product, which appears as a hght, tan homogeneous cream, is

then drawn through a suitable straining medium,

such as cheese cloth.

-Typical analytical results on the lubricating emulsion of the example are as follows:

Obtained By Analysis Theoretical Guanidine Stearate per cent.. 3. 2-3. 1 Triethanolarnine Stearate 0 {ice Triethanolamine Obviously many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scopethereof and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim: I

1. A lubricating emulsion comprising an emulsion of mineral oil-in-water, a guanidine salt of a soap-forming saturated fatty acid, and an alkylolamine salt of an aliphatic monocarboxyiic acid containing at least 10 carbon atoms, said alkylolamine salt being present in amounts sufficient to stabilize said emulsion at elevated temperatures.

2. A lubricating emulsion comprising a viscous emulsion of mineral oil-in-water, said mineral oil being within the viscosity range of 60-100 Saybolt Universal seconds at 210 F., a guanidine salt of a soap-forming saturated fatty acid, an alkylolamine salt of an aliphatic monocarboxylic acid containing at least 10 carbon atoms, and free alkylolamine, said free alkylolamine being present in amounts sufiicient to substantially inhibit steel corrosion.

, 3. A stable emulsion comprising an emulsion of mineral oil in water in which the emulsifying agent is a guanidine salt of a saturated monocarboxylic acid containing at least 10 carbon atoms.

4. A stable emulsion comprising an emulsion of mineral oil in water in which the emulsifying agent is a guanidine saltof a soap-forming saturated fatty acid.

5. An oil-in-water emulsion comprising an emulsion of mineral oil in water in which the emulsifying agent is a combination of a guanidine salt of a saturated fatty acid containing at least 10 carbon atoms, and an alkylolamine salt of a carboxylic acid containing at least 10 carbon atoms, said alkylolamine salt being present in amounts suilicient to stabilize said emulsion at elevated temperatures.

6. A stable emulsion comprising an' emulsion of mineral-in-water, a guanidine salt of a soap- OOWFN of the guanidine salt to alkyiolamine salt is greater than 1 and in which said free alkylolamine is present in amounts to substantially inhibit steel corrosion.

MALCOLM D. BRAY.

REFERENCES CITED,

The following references are of record in the file of, this patent:

Number UNITED STATES PATENTS .Name Date Ericks May 26, 1942 Hodson Mar. 28, 1944 Waugh Oct. 3, 1939 Kaufman July 18, 1944 Wilson May 23, 1944 Sullivan Nov. 10, 1931 Holtzclaw May 11, 1937 Morgan Dec. 8, 1942 Weigand Mar. 8, 1932 OTHER REFERENCES Page 159 01 vol. II 01 Gregorys book entitled Uses and Applications and Related Materials" (Copy in Div. 64.)

Pages 382 and 383 of the Organic Qhemis 20 by Fleser and Fieser (1944). (A copy in Div. 64.) 

